Here's what I do as GM, to show a larger version of a token to the players:  I select the token and touch 'z'.  I right-click the enlarged image, and do "copy image URL".  In chat, I type [img](xxx) where xxx is the pasted URL of the image, and that will show the image to the players.  You might find that the text in the URL from the ? onwards needs to be deleted to make it work.  You will probably find that if you use .webp images, you need to delete the ? onwards, and replace it with ?.png to fake the roll20 chat-handling code into just doing it.  I wouldn't mind if this was a bit easier, but I don't do it often enough that its clunkiness makes me stop using it.  (What I also do as GM is keep a separate campaign journal in a cloud document service, that the players have shared access to, and I have a prepared set of images to paste into the campaign journal as the adventure progresses.  We keep a loot spreadsheet there as well, an xp spreadsheet, a document with rules clarifications, etc.)